The Radiation Oncology Branch has entered fifteen patients onto this study of photodynamic therapy. The treatment protocol involves the intravenous administration of the Photophrin II preparation of the hematoporphyrin derivative, followed by delivery of light to the affected area. Light is directed at the tumor using optical fibers coupled to an argon pumped dye laser. When possible, laser Doppler blood flow measurements have been made on patients before and after treatment. Fifteen patients have been entered onto the protocol to date. Toxicity associated with treatment includes cutaneous photosensitivity, with one patient developing a first degree sunburn on his arms upon exposure to bright sunlight 78 days after drug infusion. Two patients with extensive recurrent breast cancer on the chest wall developed transient discomfort in the treatment area requiring narcotics for pain control. In 10 patients with recurrent disease involving the skin, complete responses have been obtained in one patient with had and neck cancer, one patient with breast cancer, and one patient with cutaneous lymphoma. Re-aeration of the lung has been achieved in two patients with lung collapse secondary to obstructing tumor in the main stem bronchus following clean up bronchoscopy to move necrotic tumor; a third patient is awaiting treatment at the time of this report. Light delivery into the peritoneal cavity at the time of exploratory laparotomy has been achieved in one patient using a specially designed light diffusing rod and a dilute solution of intralipid instilled into the peritoneal cavity at the time of surgery. Measurements of light distribution using sterile photodiodes in the abdominal cavity have been made. Preliminary analysis of the data would indicate that there is significant attenuation of light by hemoglobin present, an issue which will need to be addressed if adequate light delivery to the peritoneal surface is going to be achieved in this manner.